This invention relates generally to the field of electromagnetic shielding of electronic equipment, and particularly relates to a gasket for providing such shielding around doors, or other panels, of cabinets, or other enclosures, of electronic equipment.
Manufacturers and users of electronic equipment are now required by law to limit the amount of electromagnetic radiation emitted by such equipment. Any such stray radiation, if the levels are high enough, can interfere with the proper operation of other equipment and communications links. Further, it is usually desirable to shield a piece of electronic equipment against receiving electromagnetic interference from some source outside of its cabinet.
Therefore, it has become quite common to surround electronic components with electrically conductive cabinets or chassis, usually made of metal. Of course, such enclosures must contain openings for access to the electronic equipment therein. The openings are usually covered by a hinged door or removable panel, generally also made of metal. Since gaps resulting around the edges of such closures can allow electromagnetic energy to pass through, it is a common practice to seal the gaps with an electrically conductive gasket. Such a gasket is attached to either the equipment cabinet around the opening, or to the door or other panel around its edges.
There are many specific configurations of gaskets used for this purpose. The most common are compressable types designed to fill the gap as the door or panel is latched to the cabinet and pulled against it by some other mechanism. Examples of various specific forms of such gaskets include those made of metal spring material (such as berrilym copper), metal mesh, metal mesh surrounding a compressable elastomeric core, and a conductive elastomer strip by itself. An example of a gasket having a wire mesh around an elastomeric core is given in U.S. Pat. No. 4,652,695--Busby (1987). An example of a gasket using a conductive polymer is provided by U.S. Pat. No. 4,659,869--Busby (1987). The example gaskets of these two patents also have a clip for easy attachment to the cabinet or door.
Such compressive types of gaskets require that a separate mechanism be used to compress it by latching the door or other panel to the cabinet. These mechanisms have generally tended to be complicated, thus expensive and labor-intensive to install. Often they are not reliable in providing continuous compression at all points along the length of the gasket, which is necessary to provide an effective electromagnetic radiation seal. Therefore, other gaskets include magnetic elements which are attracted to the other of the cabinet or door from that to which the gasket is attached, in an attempt to improve the seal. Examples of different configurations of this type of gasket are given in the following U.S. Pat. Nos.: 3,260,788--Stetson (1966); 3,889,043--Ducros (1975); 3,969,572--Rostek (1976); and 4,590,710--Newland (1986).
It is a general object of the present invention to provide an electromagnetic radiation shielding gasket having improved characteristics over those of the prior art. It is a specific object of the present invention to provide a gasket that provides a better seal in situations where the gaps between the surfaces being sealed are dimensionally irregular or where the surfaces themselves are irregular. It is also an object of this invention to provide a gasket structure that can be economically and commercially manufactured in large volumes. It is yet another object of the present invention to provide a gasket that is easy to install.